Sound recording apparatus



April 1968 o. FREUDENSCHUSS 3,376,093

SOUND RECORDING APPARATUS 4 Sheets-Sheet 1 Filed March 3, 1965 millllillI-sfi T7 llrlllllllllaill r12 April 2, 1968 b. FREUDENSCHUSS 3,376,093

SOUND RECORDING APPARATUS 4 Sheets-Sheet 2 Filed March 5, 1965 April 1963 o. FREUDENSCHUSS 3,376,093

SOUND RECORDING APPARATUS 4 Sheets-Sheet :5

Filed March .3, 1965 April 2, 1968 o. FREUDENSCHUSS 3,376,093

SOUND RECORDING APPARATUS 4 Sheets-Sheet Filed March 3, 1965 WWW United States Patent 015 3,376,093 Patented Apr. 2., 1968 ice 3,376,093 SOUND RECORDING APPARATUS Otto Freudenschuss, Vienna, Austria, assignor to Karl Vockerihuber and Raimund Hauser, both of Vienna, Austria Filed Mar. 3, 1965, Ser. No. 436,775 Claims priority, application Austria, Mar. 10, 1964,

A 2,081/ 64 38 Claims. (Cl. 352-25) ABSTRACT OF THE DISCLOSURE Apparatus for recording sound on film, comprising, in combination, a mode selector switch movable between a forward, a reverse position, and a standstill position, film feed drive means responsive to the position of the mode selector switch and arranged to effect a forward movement of a film along a predetermined path in the apparatus when the mode selector switch is in the forward" position and to effect a reverse movement of the film along the path when the mode selector switch is in the reverse position, projection means responsive to the position of the mode selector switch and arranged to effect a standstill projection of a portion of the film in a predetermined position in the path when the mode selector switch is in the standstill position. A film length meteris provided for registering the amount of such reverse movement and for providing an indication when the film has subsequently performed such forward movement by the same amount. A sound recorder is provided operable to record sound on the film during such forward movement thereof, and a recording switch means is arranged to initiate the operation of the sound recorder in response to the indication by the film length meter.

This invention relates to sound recording apparatus, particularly to a motion picture projector comprising a sound recorder and a reverse motion drive.

Sound motion picture apparatus, such as sound film projectors, comprise a picture section, in which the film is intermittently driven, and a sound section, which comprises means for stabilizing the movement of the film adjacent to the sound heads. These stabilizing means comprise at least one sound roller for guiding the film, and a flywheel coupled to this roller. In most apparatus, this flywheel does not have a drive of its own and is not accelerated to its nominal speed by the film until the apparatus has been started. As a result, a certain start-up period is required until the film attains a steady state speed. Depending on the design of the apparatus, this start-up period is between and seconds. This fact is generally insignificant for the reproduction but is much disturbing during the recording of sound. A sound film is usually cut, then provided with a magnetic track and provided with sound. Only in exceptional cases can the sound be recorded in a single pass of the film. As a rule, the sound must be recorded scene by scene. In the apparatus described initially hereinbefore, this involves extremely great difficulties because the apparatus must first be operated for reproduction. When the film has attained the steady state speed in the sound section, the amplifier must be switched from reproduction to recording at the desired beginning point and the recording of sound on the film must begin, or a reproducing unit, e.g., a tape reproducing apparatus must be started at the same time. Only in rare cases will it be possible to join a sound scene to the preceding one without a gap in the recording or an erasing of a portion of the preceding scene.

There have been attempts to solve this problem. It has been suggested to provide marks on the film, such as guide-tags or notches, and to use these marks to effect an automatic switching of the amplifier. These apparatus, however, involve a very high structural expenditure and considerable labor is required for marking the film.

Other installations have been disclosed, which comprise a projector, which is driven by a synchronous motor, and a sound mechanism, which is also driven by a synchronous motor. The projector and the drive motor for the sound mechanism are jointly started and a counter is provided, which couples the sound motor to the sound mechanism after a predetermined number of frames. In magnetic sound recorders it is also known to provide two pre-settable counters for controlling various functions of the apparatus, such as high speed reverse, reproduction, etc. Finally, magnetic sound recorders for advertising purposes have been proposed, which are started by a light barrier; when a predetermined tape length has been unwound, which is adjustable at a counter, the apparatus is switched to a high speed reverse motion and is subsequently stopped.

It is an object of the present invention to provide a novel solution to the problem outlined above. This solution results in a considerable simplification in structure as well as an important improvement in operation.

It is another object of the present invention to provide a frame or time meter or counter, which is adapted to be started simultaneously with the reverse operation of the apparatus and switches the apparatus to forward motion after a number of frames or period of time before the sound recorder is energized. With this arrangement, the start-up operation of the sound reproducer is bridged and the operation of the sound recorder is not initiated until the sound carrier has attained the desired speed. With the novel apparatus, the sound can be recorded on the film by ascertaining the beginning points in standstill projection, then switching the apparatus to reverse operation and simultaneously starting the counter. When the apparatus has been stopped and switched to forward oper ation, the counter will initiate the operation of the recording amplifier at the very instant at which the preselected frame is in the picture gate of the apparatus. Thus it is possible to record sound on a film scene by scene and closely to join the various sound scenes without formation of gaps left without a recording and without erasing parts of the preceding scene.

With the above and other objects in view, which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawings, in which:

FIGURE 1 is an elevation showing a substandard film projector according to the invention; FIG. 2 is a sectional view taken on line IIII of FIG. 3 and showing a detail of the novel projector; FIG. 3 is a sectional view taken on plane IIIIII in FIG. 2;

FIGS. 4 to 8 illustrate the apparatus of FIG. 2 in different operative positions; FIGS. 9 and 10 show two elements of construction of the novel device; FIG. 11 is a block diagram; and FIG. 12 shows the switch-on curves of the erasing oscillator and the recording amplifier.

The sound film projector shown in FIG. 1 comprises in known manner a picture-reproducing section. This section comprises an illuminating device or projection means accommodated in the lamp housing 1, and a projection lens 2. The film 3 is fed through the picture-reproducing section by a pull-down claw, not shown. Behind the picture-reproducing section, the film forms a relatively large loop and finally moves through the sound section, which includes a symbolized erasing head 4 and a recording head 5. Film feed drive means in the sound section comprise a sprocket 6, which rotates at constant speed. A sound roller 7 is provided for stabilizing the film speed. A flywheel 8 is mounted on the shaft of the 3 sound roller. The film is forced by a pressure roller 9 against the sound roller 7. The sound roller 7 does not have a drive of its own but is frictionally driven by the film.

The mode selector switch for controlling the illuminating device and the film feed drive means comprises a switch handle 10. In the neutral or standstill position shown the projector is in position for standstill projection. The forward position marked V corresponds to forward operation. .The reverse position marked R corresponds to reverse operation. A milled or knurled knob 11 is provided at the end of the housing and is mounted on the drive shaft of the projector. During standstill projection, this knob 11 permits of a manual advance of the film. With the aid of the rotary knob 12, the amplifier can be energized and the modulation or sound volume can be controlled. A recording key 13 is provided on the top face of the apparatus. The key 14 operates a meter switch for starting an automatic recording control mechanism, which will be described more fully hereinafter.

The two keys 13 and 14 are secured to longitudinally slidable bars 15 and 16, respectively, which are held in their initial position, shown in FIG. 2, by springs 17 and 18. The key 13 has a projection 19, which extends under the key 14. This arrangement ensures that the key 13 will follow a depression of the key 14 whereas the key 13 can also be operated alone. The bar 16 has an elongated hole 20, through which the shaft 21 of the mode selector switch 22 extends. An auxiliary bar 23 is longitudinally slidably and pivotally mounted on the bar 16. The spring 18 acts obliquely on this auxiliary bar, which carries a pin 24 bearing on the top of an elongated hole 25 in the bar 16 and a strap 26 hearing on the bar 16. The two bars 16 and 23 are surrounded by two coaxial camwheels 27, 28 formed with cam grooves. The blocking camwheel 27 is rigidly connected to the handle of the mode selector switch. The second or holding camwheel 28 is freely rotatable on the shaft 21 and coupled to a wormwheel 29, which constitutes a film length meter. Adjacent to the wormwheel 29, a worm 31 is provided,

vwhich is mounted in a pivoted plate 30 and driven from the projector drive 3 3 without slip by a toothed belt 32 of plastics material. The plate 30 is pivoted at 34 and is held in the position shown in FIG. 2 by the spring 35. A'relatively strong spring 36acts also on the plate 30. The other end of the spring 36 is secured to the auxiliary bar 23 so that the plate 30 is pivotally moved in the clockwise sense and the worm 31 engages the wormwheel 29 in'response to a depression of the key 14.

Each of the bars and 16 carries two'switches 37, 38, 39, 40. The recording switches 37 and 39 are connected in series and so are the reproducing switches 38 v and 40. The first pair of switches are connected in circuit with the recording amplifier 41 and the erasing oscillator 42. The secondpair of switches are included in the release circuit of an external sound reproducer 43 (FIG. 11).

The blocking cam 27 connected to the handle 10 of the mode selector switch 22 comprises a labyrinth groove 44, which co-acts with a pin or blocking stop 45 mounted on the auxiliary bar 23. The groove 44 in the camwheel 27 comprises a radial release portion 44a, which is suclarger radius than the cam portions provided with the notches 47 and 48. i

When the mode selector switch is in position for standstill projection or reverse operation, the cam portion 52 of the blocking cam 27 engages a ledge 53 of the bar 15 of the recording switch so that in these conditions the guide pin 54 of the bar 15 cannot enter the lateral recess 55 of the elongated hole 56. Only during forward operation does the cam portion 52 release the ledge 53 so that the recording key 14 can move into and be retained in the recording position during forward operation.

The holding camwheel 28 connected to the wormwheel 29 has a cam portion 58, which extends from a radial groove 57 and a has a radius increasing, e.g., according to an Archimedes spiral. The cam portions 57 and 58 are intended to receive the pin or holding stop 24 of the auxiliary bar 23. The cam 60 provided on the outside periphery of the camwheel coacts with a pin 59 of the pawl lever 50 and lifts the pawl lever out of the notch 47 of the camwheel 27 in a predetermined angular position of the camwheel 28. This position corresponds to a predetermined number of revolutions of the shaft of the projector drive and consequently to a movement of the film by a length corresponding to a predetermined number of frames. When the pawl lever has been lifted out of the notch 47 of the camwheel 27, the hairpin spring 61 returns the mode selector switch to the position for standstill projection. I

The mode of operation of the novel device will be explained more fully hereinafter. When the apparatus is initially in the position shown in FIG. 2 and the key 14 is depressed, the bars 15 and 16 are moved downwardly. The auxiliary bar 23 participates in this movement, the pin 45 enters the radial groove portion 44a of the camwheel 27 and the pin 24 is outwardly displaced in the radial groove port-ion 57 of the camwheel 28. (The key 14 can only be operated when the mode selector switch is in position for standstill projection because in the positions for forward or reverse operation the pin 45 engages the outside periphery of the camwheel 27 to prevent a further displacement of the key 14.) While the key 14 is depressed, the handle 10 of the mode selector switch 22 is rotated to the position for reverse operation so that the pin 45 is guided in the arcuate portion 44b of the groove 44- of the camwheel 27 and the bar 23 and with it the key 14 are locked in their operative position. The pawl 50 enters and is retained in the notch 47 to lock the mode selector switch in position for reverse operation (see FIG. 4). In response to the depression of the key 14, the spring 36 has caused a pivotal movement of the plate 30 so that the worm 31 engages the wormwheel 29 and the latter is rotated in the counterclockwise sense.

Whereas the normally open recording switches 37 and 38 coupled to the recording key 13 are closed in this position, the circuits of the recording amplifier and of the oscillator as well as the release circuit for the sound reproducer 43 are still interrupted by the normally closed recording switches 39 and 40 controlled by the key 14.

ceeded in the clockwise sense by a blocking arcuate groove portion 44b (see FIG. 9). This groove portion 44b joins a second radial release portion 14c, which is succeeded in the clockwise sense by a wide, substantially arcuate portion or second arcuate portion 44d. A straight groove portion 442 extends outwardly from the portion 44d at an angle to the radius. The outer boundary of the groove portion 44a is of sawtooth shape and forms a notch 46 for the pin 45. Three notches 47 to 49 are provided on the outside periphery of the blocking cam 27. A pivoted pa-wl lever 50 enters these notches under the action of a spring 51. The notch 49 corresponding to forward operation is provided on a cam portion having a The rotation of the wormwheel 29 and of the camwheel 28 causes a downward displacement of the pin 24 engaging the eccentric cam portion 58. This displacement of the pin 24 results in a movement of the auxiliary bar 23 relative to the bar 16. As a result, the pin 45 is also downwardly displaced in the radial groove portion of the camwheel 27.. When the wormwheel 29 has been rota-ted through about 250 (corresponding to a period of about 10 seconds), the cam 60 of the camwheel 28 lifts the pawl lever 50 by means of the pin 59 out of the notch 47 of the camwheel.

This position corresponding to the final position of the film length meter is shown in FIG. 5. Under the action of the hairpin spring 61 (*FIG. 3), the mode selector switch is now returned in theclockwise sense to the position for standstill projection. This position is shown in FIG. 6.

shaped notch 46 in the arcuate groove portion 44d so that the mode selector switch 22 cannot be moved in the counterclockwise sense (to the position for reverse operation).

When the mode selector switch is moved in the clockwise sense .to the position for forward operation (FIG. 7), the pin 45 enters and is retained in the groove Me, which deviates from the radial direction. At the same time, the cam 52 releases the ledge 53 of the bar so that the latter is pivotally moved by the spring 17 and the guide pin 54 enters the lateral recess 55 of the elongated hole 56. In the position for forward operation, the mode selector switch 22 is locked by the pawl 50 entering the notch 49 of the camwheel 27. As the notch 49 is arranged on a peripheral portion which has a larger radius than the peripheral portion-s provided with the notches 47 and 48, the cam 60 of the camwheel 28 does not act on the pawl 50 in this position. By the rotation of the worm wheel 29 in the clockwise sense, the pin 24 and with it the auxiliary bar 23, are returned upwardly. As the groove portion 44e of the camwheel 27 deviates from the radial direction, the auxiliary bar 23 is deflected in the counterclockwise sense against the action of the spring 18 by the pin 45 sliding upwardly in the groove portion Me. (The arrangement is shown in an intermediate position in FIG. 7.) After a further rotation the wormwheel and of the camwheel in the clockwise sense to their initial position, the radial portion 57 of the cam finally receives the pin 24. The spring 18 can now displace the auxiliary bar 23 and the bar 16 upwardly and when the pin 45 has moved out of the groove portion Me, the auxiliary bar is also pivotally moved back to its initial position. By the displacement of the bar 16-, the worm 31 is disengaged from the wonmwheel 29 so that the latter stops. At the same time, the key 14 returns to its initial position. The key 13 remains in its operative position because the b-ar 15 is retained by the guide pin 54 (see also FIG. 8). In this position, the switches 3-7 and 39, as well as 38 and 40 are closed so that the recording amplifier 41 and the erasing oscillator 42 as well as a magnetic sound reproducer 43 are energized.

The recording may be terminated by a pivotal movement of the mode selector switch 22 to the position for standstill projection. The cam 52 of the camwheel 27 causes by means of the ledge 53 a pivotal movement of the bar 15 to the left so that the pin 54 leaves the recess 55 ofthe elongated hole 56. The spring 17 returns the bar 15 and with it the key to the initial position, and the switches 37 and 38 interrupt the recording circuits.

As the movement of the film from the starting of the forward operation to the energization of the recording amplifier 41 and of the erasing oscillator 42 corresponds to the same number of frames as the movement of the film during the preceding reverse operation, the recording amplifier 41 is energized just at the selected beginning point. This number of frames is selected so that the flywheel of the projector has certainly attained its steadystate angular speed when the recording amplifier is energized.

Normal magnetic sound reproducers are immediately ready for operation when their release circuit has been closed. When the new projector is to be used with reproducing apparatus having a relatively long energization delay, the switch 40 may be closed before the switch 39 rather than simultaneously with it. To this end, the switch 40 may be controlled by the cam wheel 28.

As the erasing head and the recording head are staggered for design reasons (distance a in FIG. 1), it is recommendable to energize the erasing circuit before the recording circuit in accordance with the time required by the film to move from the erasing head to the recording head. This may also be effected by the camwheel or a time-limit relay. 7

In another embodiment the erasing oscillator and receiving amplifier are energized simultaneously but the re- Cir cording circuit includes time constant networks, which cause an appropriately slow rise of the level of the recording current. In FIG. 12, the switch-on curve of the erasing circuit is indicated at 65, that of the recording circuit at 66. The current value is plotted along the ordinate in percent of the normal value and the time is plotted along the abscissa.

v is the film speed, a the distance between the erasing and recording heads. Thus a/ v is the time required by the film to move from the erasing head to the recording head.

The invention is not restricted to the embodiment shown. For instance, a counter which is responsive to the number of frames of the length by which the film is fed may be replaced by a time meter.

The counter for forward and reverse movements may be replaced by a counter for a single direction of movement.

While I have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

What is claimed is:

1. Apparatus for recording sound on film, comprising, in combination, a mode selector switch movable between a forward position, a reverse position, and a standstill position, film feed drive means responsive to the position of said mode selector switch and arranged to effect a forward movement of a film along a predetermined path in said apparatus when said mode selector switch is in said forward position and to effect a reverse movement of said film along said path when said mode selector switch is in said reverse position, projection means responsive to the position of said mode selector switch and arranged to effect a standstill projection of a portion of said film in a predetermined position in said path when said mode selector switch is in said standstill position, a film length meter for registering the amount of such reverse movement and for giving an indication when said film has subsequently performed such forward movement by the same amount, a sound recorder operable to record sound on said film during such forward movement thereof, and recording switch means arranged to initiate the operation of said sound recorder in response to said indication by said film length meter.

2. Apparatus as set forth in claim -1, in which said film length meter is a film frame counter.

3. Apparatus as set forth in claim 1, in which said film feed drive means are operable to effect such forward and reverse movements of said film at a predetermined speed and said film length meter is a time meter.

4. Apparatus as set forth in claim 1, which comprises a sound recorder and recording switch means responsive to said film length meter for initiating the operation of said sound recording when the amount of such forward movement is in a predetermined relation to the amount of the previous reverse movement of said film.

5. Apparatus as set forth in claim 4, in which said recording switch means are arranged to initiate the operation of said sound recorder when such forward movement is smaller by a predetermined amount than the predetermined reverse movement of said film.

6. Apparatus as set forth in claim 1, in which said film length meter comprises a counter, which is arranged to change its count in one sense during such reverse movement of said film and to change its count in the opposite sense during such forward movement of said film and to give said indication when its count is the same as before said reverse movement of said film.

7. Apparatus as set forth in claim 1, which comprises locking means for preventing an initiation of the operation of said film length meter when said film is in movement.

8. Apparatus as set forth in claim 1, which comprises locking means which prevent a movement of said mode selector switch to said forward position when said film length meter is in operation.

9. Apparatus as set forth in claim 1, which comprises switch means responsive to said film length meter and arranged to de-energize said film feed drive means when a predetermined amount of such reverse movement has been performed.

10. Apparatus as set forth in claim 1, which comprises means for moving said mode selector switch out of said reverse position in response to said film length meter when a predetermined amount of such reverse movement has been performed.

11. Apparatus as set forth in claim 1, which comprises spring means tending to move said mode selector switch out of said reverse position, a pawl adapted to hold said mode selector switch in said reverse position, and means responsive to said film length meter and arranged to disengage said pawl from said mode selector switch when a predetermined amount of such reverse movement has been performed.

-12. Apparatus as set forth in claim 1, in which said mode spring means tends to move said mode selector switch to a neutral position between said reverse and forward positions.

13. Apparatus as set forth in claim 12, in which said neutral position is identical with said standstill position.

14. Apparatus as set forth in claim 1, which com-prises a meter switch movable from an inoperative position to an operative position for initiating the operation of said film length meter, spring means tending to move said meter switch to said inoperative position, and holding means responsive to said film length meter and arranged to hold said meter switch in said operative position unless said film length meter is in a predetermined initial position.

15. Apparatus as set forth in claim 14, in which said recording switch means comprise a normally open recording switch and a normally closed recording switch connected in series, said meter switch comprises a driver arranged to close said normally open recording switch in response to a movement of said meter switch to said operative position, said normally closed recording switch is arranged to be open when said meter switch is in said operative position, and recording switch holding means are arranged to hold said normally open recording switch in its closed position when said mode selector switch is in said forward position.

16. Apparatus as set forth in claim 15, in which said recording switch holding means are arranged to hold said normally open recording switch in its closed position when, and only when said mode selector switch is in said forward position.

17. Apparatus as set forth in claim 14, in which said holding means comprise a holding camwheel coupled to said film length meter.

18. Apparatus as set forth in claim 17, in which said meter switch comprises a longitudinally slidable slide bar under the action of said spring means and said holding camwheel is arranged to prevent a movement of said bar to said inoperative position unless said meter is in said initial position.

19. Apparatus as set forth in claim 18, in which said slide bar carries a holding stop and said holding camwheel has a release portion, which extends in the direction of movement of said slide bar and is adjacent to said holding stop when said meter is in said initial position.

20. Apparatus as set forth in claim 19, in which said release portion extends along a radius of said holding camwheel.

21. Apparatus as set forth in claim 17, in which said film length meter comprises a worm coupled to said film feed drive means and a wormwheel coupled to said camwheel and in mesh with said Worm.

22. Apparatus as set forth in claim 21, in which said wormwheel and camwheel are integral.

23. Apparatus as set forth in claim 14, which comprises a blocking camwheel coupled to said mode selector switch and arranged to prevent a movement of said meter switch from said inoperative position to said operative position unless said mode selector switch is in said standstill position.

24. Apparatus as set forth in claim. 23, in which said meter switch comprises a longitudinally slidable slide bar which is under the action of said spring means and carries a blocking stop and said blocking camwheel comprises a release portion which extends in the direction of move ment of said slide bar and is adjacent to said blocking stop when said mode selector switch is in said standstill position.

25. Apparatus as set forth in claim 24, in which said release portion extends along a radius of said blocking camwheel.

26. Apparatus as set forth in claim 24, in which said release portion is formed by a guide groove portion.

27. Apparatus as set forth in claim 26, in which said release portion is continued at one end by a blocking arcuate groove portion arranged to prevent a movement of said mode selector switch other than to said reverse position when said meter switch is in said operative position and said blocking stop means is in said blocking arcuate groove portion.

28. Apparatus as set forth in claim 27, in which said holding means comprise a holding camwheel coupled to said film length meter and facing said blocking camwheel, said slide bar carries a holding stop urged by said spring means towards said holding camwheel, said holding carnwheel has a release portion which extends in the direction of said slide bar and is adjacent to said holding stop when said meter is in said initial position, said blocking arcuate groove portion is continued at the end opposite to said release portion by a second release portion extending in the direction of movement of said slide bar, arranged to receive said blocking stop when said mode selector switch is in said reverse position, and continued by a second arcuate groove portion having a smaller radius than said blocking arcuate groove portion, said holding camwheel is formed with a wall portion which is eccentric with respect to said blocking camwheel and arranged to engage said holding stop and to displace said blocking stop radially inwardly in said second release portion to release said mode selector switch for a movement out of said reverse position when said blocking stop is in said second release portion and said meter switch is in said operative position.

29. Apparatus as set forth in claim 28, in which said mode selector switch is movable to a neutral position between said reverse and forward positions and said second arcuate groove portion is formed with a notch arranged to receive said blocking stop when said mode selector switch is in said neutral position, and to block said mode selector switch against a movement to said reverse position when said blocking stop is in said notch.

30. Apparatus as set forth in claim 29, in which said notch is sawtooth-shaped.

31. Apparatus as set forth in claim 29, which comprises spring means tending to move said mode selector switch from said reverse position to said neutral position, a pawl adaptedto hold said mode selector switch in said reverse position, and means responsive to said film length meter and ar-ranged'to disengage said pawl from said mode selector switch when a predetermined amount of such reverse movement has been performed.

32. Apparatus as set forth in claim 31, in which said neutral position is identical with said standstill position.

33. Apparatus as set forth in claim 28, in which said second arcuate groove portion is continued by a further groove portion which is inclined with respect to said direction of movement of said slide bar and adapted to receive said blocking stop when said mode selector switch is in said forward position and said meter switch is in said operative position, said blocking stop is carried by an auxiliary bar pivoted to said slide bar, and said holding camwheel is arranged to move said slide bar against the action of said spring means when said mode selector switch is in said forward position and said meter switch is in said operative position and thus to move said blocking stop in said further groove portion with pivotal movement of said auxiliary bar until said blocking stop has reached an initial position when said film length meter is in its initial position.

34. Apparatus as set forth in claim 17, in which said holding means comprise a holding camwheel coupled to said film length meter and facing said blocking camwheel.

35. Apparatus as set forth in claim 34, in which said holding and blocking camwheels are coaxial.

36. Apparatus as set forth in claim 1, in which said film feed drive means are adapted to effect said forward movement of said film at a predetermined speed and in which said sound recorder comprises an erasing head operable to erase previous sound recordings on said film and a recording head succeeding said erasing head in the direction of movement of said film along said path and operable to record sound on said film, said recording switch means comprise an erasing head switch adapted to initiate the operation of said erasing head and a recording head switch adapted to initiate the operation of said recording head, and means for controlling said erasing head switch and said recording head switch in response to said indication of said meter so that the operation of said recording head is initiated after the initiation of the operation of said erasing head with a delay which corresponds to the time required by the film to move from the erasing head to said recording head at said predetermined speed.

37. Apparatus for recording sound on film, comprising, in combination, a mode selector switch movable between forward and reverse positions, feed drive means responsive to the position of said mode selector switch and arranged to effect a forward movement of a film along a predetermined path in said apparatus when said mode selector switch is in said forward position and to effect a reverse movement of said film along said path when said mode selector switch is in said reverse position, a length meter for registering the amount of such reverse movement and for giving an indication when said film has subsequently performed such forward movement by the same amount, a sound recorder operable to record sound on said film during such forward movement thereof, and recording switch means arranged to initiate the operation of said sound recorder in response to said indication by said length meter.

38. Apparatus for recording sound on film, comprising, in combination, a mode selector switch movable between forward and reverse positions, feed drive means responsive to the position of said mode selector switch and arranged to effect a forward movement of a film along a predetermined path in said apparatus when said mode selector switch is in said forward position and to effect a reverse movement of said film along said path when said mode selector switch is in said reverse position, a length meter for registering the amount of such reverse movement and for giving an indication when said film has subsequently performed such forward movement by the same amount, a sound recorder operable to record sound on said film during such forward movement thereof, recording switch means arranged to initiate the operation of said sound recorder in response to said indication by said length meter, a sound reproducer energizable to reproduce sound signals, and reproducing switch means responsive to said length meter for initiating the operation of said sound reproducer when the amount of such forward movement is in a predetermined relation to the amount of the previous reverse movement of said film.

References Cited UNITED STATES PATENTS 2,071,044 2/1937 Savage 3525 2,512,432 6/1950 Kolb et al. 352-5 2,870,975 1/1959 Albee et 211. 3,140,360 7/ 1964 Whitworth. 3,196,454 7/1965 Fine 3525 JULIA E. COINER, Primary Examiner. 

